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Interview question · Application & API Security

Review an endpoint that lets an assistant fetch documents by ID, find the authorisation bug, and fix it with tests.

The commonest serious bug in AI tools is the oldest: fetching an object by ID without checking who is asking. The scored answer finds it, fixes it at the data access, and tests across users and tenants.

mediumNewPreparation tags: Microsoft, Salesforce, GoogleUpdated Nov 2026

The commonest serious bug in AI tools is the oldest: fetching an object by ID without checking who is asking. The scored answer finds it, fixes it at the data access, and tests across users and tenants.

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What would you say before reading the answer?

  1. 01 State the assumptions your answer depends on.
  2. 02 Explain the mechanism and choose a control.
  3. 03 Name a condition that would change your decision.

The worked answer includes an approach, scoring criteria and follow-up questions. Compare the reasoning with your own.

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What if · the follow-ups in this answer

The answer works through 6 follow-ups like an interviewer would

An endpoint GET /documents/{id} returns any document whose ID the caller supplies, and an AI assistant calls it with IDs the model chooses.

  1. What is the vulnerability?
  2. Why does the assistant make it worse?
  3. How should the check work?
  4. Should 'not found' and 'forbidden' differ?
  5. How do you make sure it stays fixed?
  6. How would you fix it?

Each rung has a nudge, a model answer, the principle that carries over and the weak answer to avoid. Premium opens every answer and ladder.

UP NEXT ON YOUR JOURNEY
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